Nitrile-substituted silanes and electrolyte compositions and electrochemical devices containing them

ABSTRACT

Described herein are liquid, organosilicon compounds that including a substituent that is a cyano (—CN), cyanate (—OCN), isocyanate (—NCO), thiocyanate (—SCN) or isothiocyanate (—NCS). The organosilicon compounds are useful in electrolyte compositions and can be used in any electrochemical device where electrolytes are conventionally used.

CROSS-REFERENCE TO RELATED APPLICATIONS

Priority is hereby claimed to provisional application Ser. No.61/830,851, filed Jun. 4, 2013, which is incorporated herein byreference.

BACKGROUND

Liquid electrolytes in Li-ion batteries conventionally comprise alithium salt, usually LiPF₆, in an organic solvent blend of ethylenecarbonate (EC) and one or more co-solvents such as dimethyl carbonate(DMC), diethyl carbonate (DEC), or ethylmethyl carbonate (EMC).Unfortunately, LiPF₆ is unstable in these carbonate solvents above 60°C., as well as at charge voltages above 4.3 volts. Operation of a Li-ionbattery above these temperatures or voltages results in rapiddegradation of electrode materials and battery performance. In addition,current Li-ion electrolyte solvents exhibit flashpoints around 35° C.,and are the major source of the energy released during an extreme Li-ioncell failure. Given these significant limitations, current electrolytesare impeding the development of advanced Li-ion batteries for all uses,including portable products, electric drive vehicles (EDVs), and utilityscale use. A dramatic reduction in battery failure rate is also requiredfor large scale Li-ion batteries to effectively serve applications inEDVs and grid storage.

Thus, there is a long-felt and unmet need for improved electrolytesolutions in energy storage devices such as Li-ion batteries.

SUMMARY OF THE INVENTION

Disclosed herein are organosilicon (OS) compounds for use as electrolytesolvents in electrochemical devices, among other uses.

In general, OS compounds are environmentally friendly, non-flammable,high temperature-resistant materials. These characteristics make OSmaterials well-suited for use as electrolyte solvents, binders, andcoatings in energy storage devices. OS-based electrolytes are compatiblewith all lithium (Li) based electrochemical systems, including primaryand rechargeable batteries, (i.e. Li-ion, Li-air), and capacitors (i.e.super/ultra-capacitors). The process of designing OS-based electrolytesinto a Li battery involves limited changes in the cell design, and theseelectrolytes can be incorporated into production operations withexisting manufacturing processes and equipment.

The OS compounds described herein can be used as liquid electrolytesolvents that replace the carbonate based solvent system in traditionalLi-ion batteries. The OS-based solvents provide significant improvementsin performance and abuse tolerance in Li-ion batteries, includingincreased thermal stability for longer life at elevated temperatures,increased electrolyte flash points for improved safety, increasedvoltage stability to allow use of high voltage cathode materials andachieve higher energy density, reduced battery failure rates forconsistency with the requirements for large scale Li batteries used inEDV and grid storage applications, and compatibility with materialscurrently in use in Li-ion batteries for ease of adoption in currentdesigns. Electrical double-layer capacitor (EDLC) devices have alsodemonstrated functionality with OS based electrolytes. The OS compoundsdescribed herein can be used in OS-based electrolyte blends to meet therequirements of specific applications in the industrial, military, andconsumer product devices.

The objects and advantages of the compounds and electrolyte formulationswill appear more fully from the following detailed description andaccompanying drawings.

Disclosed herein are compounds of Formula I or Formula II:

wherein R¹, R², and R³ are the same or different and are independentlyselected from the group consisting of C₁ to C₆ linear or branched alkyland halogen;

“Spacer” is absent or is selected from the group consisting of C₁ to C₆linear or branched alkylene, alkenylene, or alkynylene, provided thatwhen “Spacer” is absent, Y is present;

Y is absent or is selected from the group consisting of—(O—CH₂—CH₂)_(n)— and

wherein each subscript “n” is the same or different and is an integerfrom 1 to 15, and subscript “x” is an integer from 1 to 15; and

each R⁴ is the same or different and is selected from the groupconsisting of cyano (—CN), cyanate (—OCN), isocyanate (—NCO),thiocyanate (—SCN) and isothiocyanate (—NCS).

Also specifically disclosed herein are compounds of Formula I, wherein“Spacer” is present, and Y is —(O—CH₂—CH₂)_(n)—. Additionally,specifically disclosed herein are compounds in which “Spacer” is presentand Y is

Additionally disclosed herein are compounds in which “Spacer” is absent,and Y is —(O—CH₂—CH₂)_(n)—.

Also disclosed herein are compounds having a structure as shown in anyof Formulas II, III, IV, and V:

wherein R¹, R², and R³ are the same or different and are independentlyselected from the group consisting of C₁ to C₆ linear or branched alkyland halogen; “spacer” is a C₁ to C₆ linear or branched alkylene,alkenylene, or alkynylene; each R⁴ is the same or different and isselected from the group consisting of cyano (—CN), cyanate (—OCN),isocyanate (—NCO), thiocyanate (—SCN) and isothiocyanate (—NCS); eachsubscript “n” is the same or different and is an integer from 1 to 15;“x” is an integer from 1 to 15. Also included herein are electrolytecompositions comprising one or more of the compounds of Formulas I, II,III, IV, V, as described herein, in combination with a salt, preferablya lithium-containing salt.

R¹, R², and R³ may optionally be selected from the group consisting ofC₁ to C₃ alkyl, chloro, and fluoro; and R⁴ may optionally be cyano.

When the compound comprises Formula II, R¹ and R³ may optionally beselected from the group consisting of C₁ to C₃ alkyl (or simply methyl),chloro, and fluoro. Each “n” is optionally and independently an integerfrom 1 to 5. R⁴ may optionally be cyano.

When the compound comprises Formula III, R¹, R², and R³ may optionallybe selected from the group consisting of C₁ to C₃ alkyl, chloro, andfluoro. In some versions of the Formula II compounds at least one of R¹,R², and R³ is halogen; in other versions of the Formula II compounds atleast two of R¹, R², and R³ are halogen. The “spacer” may optionally bea C₂ to C₄ linear or branched alkylene. R⁴ may optionally be cyano.

When the compound comprises Formula IV, R¹, R², and R³ may optionally beselected from the group consisting of C₁ to C₃ alkyl, chloro, andfluoro. In some versions of the Formula II compounds at least one of R¹,R², and R³ is halogen; in other versions of the Formula II compounds atleast two of R¹, R², and R³ are halogen. The “spacer” may optionally bea C₂ to C₄ linear or branched alkylene. R⁴ may optionally be cyano. Incertain versions of the Formula II compounds, “x” may optionally be 1 to4.

When the compound comprises Formula V, R¹, R², and R³ may optionally beselected from the group consisting of C₁ to C₃ alkyl, chloro, andfluoro. In some versions of the Formula II compounds at least one of R¹,R², and R³ is halogen; in other versions of the Formula II compounds atleast two of R¹, R², and R³ are halogen. The “spacer” may optionally bea C₂ to C₄ linear or branched alkylene. R⁴ may optionally be cyano. Incertain versions of the Formula II compounds, “x” may optionally be 1 to4.

In all versions of the compounds, “halogen,” includes fluoro, chloro,bromo, and iodo. Fluoro and chloro are the preferred halogensubstituents. The term “lithium-containing salt” explicitly includes,but is not limited to, LiClO₄, LiBF₄, LiAsF₆, LiPF₆, LiCF₃SO₃,Li(CF₃SO₂)₂N, Li(CF₃SO₂)₃C, LiN(SO₂C₂F₅)₂, lithium alkylfluorophosphates and lithium bis(chelato)borates.

Also disclosed herein are electrolyte compositions comprising one ormore organosilicon compounds as recited in the preceding paragraphs.Also disclosed herein are electrochemical devices comprising suchelectrolyte compositions. The compounds disclosed herein are highlyuseful for formulating electrolytes for use in charge-storage devices ofall kinds (e.g., cells, batteries, capacitors, and the like).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A depict the oxidation stability of F1S₃MN with LiPF₆, LiBF₄, orLiTFSI in current density (mA/cm²) versus voltage (V vs. Li/Li⁺). FIG.1B depicts a close-up of the same data shown in FIG. 1A.

FIG. 2A and FIG. 2B depict duplicate runs to measure the reductionstability of F1S₃MN with LiPF₆, LiBF₄, or LiTFSI in current density(mA/cm²) versus voltage (V vs. Li/Li⁺).

FIG. 3A depicts the oxidation stability of F1S₃MN or F1S₃M2 with 1MLiPF₆ in current density (mA/cm²) versus voltage (V vs. Li/Li⁺). FIG. 3Bdepicts a close-up of the same data shown in FIG. 3A.

FIG. 4 depicts the reduction stability of F1S₃MN or F1S₃M2 with 1M LiPF₆in current density (mA/cm²) versus voltage (V vs. Li/Li⁺).

FIGS. 5A and 5B depict the thermal stability of F1S₃MN with LiPF₆. FIG.5A depicts a close-up of the same data shown in FIG. 5B.

FIG. 6 depicts the thermal stability of F1S₃M2 with LiPF₆.

FIG. 7 depicts the thermal stability of F1S₃MN with LiTFSI.

FIG. 8 depicts the thermal stability of F1S₃MN with LiBF₄.

FIG. 9 depicts the thermal stability of neat F1S₃MN.

FIG. 10 depicts the thermal stability of DF1S₃MN with 20% EC andVC/LiBOB.

FIG. 11 depicts the enhanced stability of F1S3MN electrolytes comparedto carbonate control electrolyte heated with de-lithiated NCA cathode.

FIG. 12 depicts the discharge capacity of cells containing variouselectrolyte solvents at a variety of C-rates at 30° C.

FIG. 13 depicts the construction of a test cell.

FIG. 14 depicts the discharge capacity of cells containing the sameelectrolyte solvents shown in FIG. 12 at a variety of C-rates at 55° C.

FIG. 15 depicts the construction of an EDLC device.

FIG. 16 depicts the performance of an EDLC device containing DF1S2MNelectrolyte with TEA-BF4.

FIG. 17 depicts the performance of an EDLC device containing variouselectrolyte solvents with TBP-PF6.

FIG. 18 depicts the oxidation stability of 1ND1N with 1M LiPF₆ or 1MLiTFSI in current density (mA/cm²) versus voltage (V vs. Li/Li⁺).

FIG. 19 depicts the reduction stability of 1ND1N with 1M LiPF₆ or 1MLiTFSI in current density (mA/cm²) versus voltage (V vs. Li/Li⁺).

FIGS. 20A and 20B depict current density (mA/cm²) versus voltage (V vs.Li/Li⁺) for cycling scans with 1ND1N and 1M LiPF₆ or 1M LiTFSI from 0 to6 V and from 6 to 0 V. FIG. 20A depicts a first cycle. FIG. 20B depictsa second cycle.

FIG. 21A depicts the oxidation stability of F1S₃MN or 1ND1N with 1MLiPF₆ in current density (mA/cm²) versus voltage (V vs. Li/Li⁺). FIG.21B depicts a close-up of the same data shown in FIG. 21A.

FIG. 22A depicts the oxidation stability of F1S₃MN or 1ND1N with 1MLiTFSI in current density (mA/cm²) versus voltage (V vs. Li/Li⁺). FIG.22B depicts a close-up of the same data shown in FIG. 22A.

FIG. 23 is a mass spectrum illustrating the thermal stability of neat1ND1N.

FIG. 24 is a mass spectrum illustrating the thermal stability of 1ND1Nwith LiPF₆.

FIG. 25A depicts a close-up of the mass spectrum profile as describedwith respect to FIG. 24 from 24-30 m/z. FIG. 25B depicts a close-up ofthe mass spectrum profile as described with respect to FIG. 24 from49-55 m/z.

FIG. 26 depicts the thermal stability of 1ND1N with LiTFSI, vinylenecarbonate (VC) and lithium bis(oxalato)borate (LiBOB).

FIG. 27 depicts the thermal stability of 1ND1N with LiBF₄.

FIG. 28 depicts the discharge capacity of cells containing variouselectrolytes at a variety of C-rates.

FIG. 29 depicts the discharge capacity of cells containing various otherelectrolyte solvents comparing the first cycle to the 50^(th) cycle.

FIG. 30A depicts the discharge capacity of cells containing a1ND1N-LiPF₆-based electrolyte at a variety of C-rates. FIG. 30B depictsthe discharge capacity of cells containing a 1ND1N-LiTFSI-basedelectrolyte at a variety of C-rates.

FIG. 31 is the ¹H-NMR spectrum (in CDCl₃) of 1ND1N with peakassignments.

FIG. 32 is the ¹H-NMR spectrum (in CDCl₃) of F1S₃MN with peakassignments.

FIG. 33 is the ¹H-NMR spectrum (in CDCl₃) of DF1S₂MN with peakassignments.

FIG. 34 is the ¹H-NMR spectrum (in CDCl₃) of DF1S₃MN with peakassignments.

FIG. 35 is the ¹H-NMR spectrum (in CDCl₃) of F1S₃cMN with peakassignments.

FIG. 36 is the ¹H-NMR spectrum (in CDCl₃) of 1S₃MN with peakassignments.

DETAILED DESCRIPTION OF THE INVENTION

Throughout the description, a number of shorthand abbreviations will beused to designate various organo silicon compounds more easily. Thefollowing conventions are used:

The nNDnN compounds have the general formula:

wherein R¹ and R³ are the same or different and are independentlyselected from the group consisting of C₁ to C₆ alkyl, each R² is thesame or different and is independently selected from the groupconsisting of cyano (—CN), cyanate (—OCN), isocyanate (—NCO),thiocyanate (—SCN) and isothiocyanate (—NCS), and the two subscripts “n”are integers that are the same or different and independently range from1 to 15. Thus, for example, 1ND1N is the compound wherein R¹ and R³ aremethyl (i.e., C₁) and both subscripts “n” are 1.

The FnSnMN compounds have the general formula:

wherein R¹, R², and R³ are the same or different and are independentlyselected from the group consisting of C₁ to C₆ alkyl (preferably methyl)and halogen (preferably F), “spacer” is a C1 to C6 linear or brancheddivalent hydrocarbon (i.e., alkylene, alkenylene, alkynylene), and R⁴ isselected from the group consisting of cyano (—CN), cyanate (—OCN),isocyanate (—NCO), thiocyanate (—SCN) and isothiocyanate (—NCS). Thecompounds designated SnMN have the same structure, wherein R¹, R², andR³ are the same or different and are independently selected from thegroup consisting of C₁ to C₆ alkyl (preferably methyl).

Related compounds disclosed herein have the structures:

wherein R¹, R², and R³ are the same or different and are independentlyselected from the group consisting of C₁ to C₆ alkyl (preferably methyl)and halogen (preferably F), “spacer” is a C1 to C6 linear or brancheddivalent hydrocarbon (i.e., alkylene, alkenylene, alkynylene), R⁴ isselected from the group consisting of cyano (—CN), cyanate (—OCN),isocyanate (—NCO), thiocyanate (—SCN) and isothiocyanate (—NCS), and “x”is an integer of from 1 to 15, preferably from 1 to 4.

The compounds disclosed herein can be made by a number of differentroutes. A general approach that can be used to fabricate the compoundsis as follows:

The various R groups are as defined herein; “n” is a positive integer.

The compounds disclosed herein can also be fabricated via the followingapproach:

The compounds disclosed herein are also made by a number of specificroutes, including the following reaction schemes:

(R⁴ as defined above) and

LiTFSI is a commercial product supplied by several internationalsuppliers:

The elements and method steps described herein can be used in anycombination whether explicitly described or not.

All combinations of method steps as used herein can be performed in anyorder, unless otherwise specified or clearly implied to the contrary bythe context in which the referenced combination is made.

As used herein, the singular forms “a,” “an,” and “the” include pluralreferents unless the content clearly dictates otherwise.

Numerical ranges as used herein are intended to include every number andsubset of numbers contained within that range, whether specificallydisclosed or not. Further, these numerical ranges should be construed asproviding support for a claim directed to any number or subset ofnumbers in that range. For example, a disclosure of from 1 to 10 shouldbe construed as supporting a range of from 2 to 8, from 3 to 7, from 5to 6, from 1 to 9, from 3.6 to 4.6, from 3.5 to 9.9, and so forth.

All patents, patent publications, and peer-reviewed publications (i.e.,“references”) cited herein are expressly incorporated by reference tothe same extent as if each individual reference were specifically andindividually indicated as being incorporated by reference. In case ofconflict between the present disclosure and the incorporated references,the present disclosure controls.

It is understood that the compounds and compositions disclosed hereinare not confined to the particular construction and arrangement of partsherein illustrated and described, but embraces such modified formsthereof as come within the scope of the claims.

The presently disclosed compounds are organosilicon compounds having ashared structural feature in the form of a one or more terminalsubstituents that comprise a carbon-nitrogen double or triple bond, suchas a cyano (R—C≡N), cyanate (R—O—C≡N), isocyanate (R—N═C═O), thiocyanate(R—S—C≡N), and/or isothiocyanate (R—N═C═S). Included among the preferredcompounds are the following structures:

The above structures are all depicted with a terminal cyano group. Thisis for purposes of brevity only. The analogous compounds having aterminal cyanate, isocyanate, or thiocyanate moiety in place of thecyano moiety are explicitly within the scope of the disclosure.Likewise, the halogenated compounds are depicted above as fluorinatedcompounds. The analogous compounds having other halogen substituents(chlorine, bromine, and/or iodine) in place of fluorine atoms areexplicitly within the scope of the present disclosure. For each compoundlisted, two alternative systematic names are provided (the first of eachpair of names designates the fundamental core as a nitrile; the seconddesignated the fundamental cores as silane.) Additionally, each compoundhas been given a short-hand designation in which DF=difluoro,TF=trifluoro, and “Sn” designates the alkylene spacer between thesilicon atom and the terminal cyanate, isocyanate, or thiocyanate moietyand “n” represents the number of carbon atoms in the spacer. Thephysical properties of selected organosilicon (OS) compounds arepresented in Table 1.

As shown in Table 1, Reduced viscosity, higher conductivity, and lowerflash point with added fluorine and reduced spacer length. DF1S₂MN haslowest viscosity and highest conductivity.

TABLE 1 Physical Properties (with 20% EC, additives, 1M LiPF₆)Properties of Neat Solvent Properties of Electrolytes with 1M LiPF₆ Di-Flash electric 30° C. 30° C. Flash MW Point Constant B.P. Co-Conductivity Viscosity Point Solvent (g/mol) (° C.) (neat) (° C.)solvent (mS/cm) (cP) (° C.) 1S₃MN 141  72 12.6 200 Not compatible withEC F1S₃MN 145  82 16.8 249 20% EC 3.5  9.1  82 F1S₃cMN 159  80 16.6 n/a20% EC 2.6 10.6 n/a DF1S₃MN 149  78 18.2 202 20% EC 4.8  8.2  78 DF1S₂MN135  64 19.5 182 20% EC 5.8  6.9  64 F1S₃M2 238 112  7.2 233 20% EC 3.014.0 112

The physical properties of neat 1ND2, 1ND1, 1ND1N and F1S₃MN, as well aselectrolyte solutions containing these solvents, are shown in Table 2:

TABLE 2 Physical Properties of Solvents and Electrolytes Properties ofNeat Solvent Properties of Electrolytes with 1 M Salt RT FlashDi-electric Batch, 30° C. 30° C. Flash Visc. Point Constant B.P.Co-solvent, Conductivity Viscosity Point Solvent (cP) (° C.) (neat) (°C.) Salt (mS/cm) (cP) (° C.) 1ND1N 8.3 168 30 n/a ZP791 1.9 33 80 20% ECLiPF₆ ZP779 1.3 29 72 ZP780 LiPF₆ ZT778 1.1 37 166 LiTFSI 1ND1 n/a 858.1 n/a CP630 4.5 5.1 52 20% EC LiPF₆ 1ND2 3.5 138 6.4 288 CP597 3.912.5 130 20% EC LiPF6 F1S₃MN 2.0 82 16.8 249 ZP82₆ 3.5 9.1 82 20% ECLiPF₆ ZP825 2.7 8.3 58 LiPF₆

In addition to the organosilicon compounds disclosed herein, the presentelectrolyte compositions may include conventional non-siliconco-solvents. For example, the present electrolyte compositions mayinclude nitriles and carbonates, such as acetonitrile, ethylenecarbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), orethylmethyl carbonate (EMC). The instant electrolyte compositions mayinclude non-silicon co-solvents at a wide range of concentrations,including but not limited to, about 1 wt % to about 40 wt %. Examples ofsuitable co-solvent concentrations include about 1 wt %, about 5 wt %,about 10 wt %, about 15 wt %, about 20 wt %, about 25 wt %, about 30 wt%, about 40 wt % or a range between and including any of the precedingamounts.

EXAMPLES

F1S₃MN Synthesis:

Scheme 1 depicts a synthesis scheme for F1S₃MN. [F] indicates afluorinating agent, such as HF, NH₄FHF, or other fluorinating agent.NH₄FHF is preferably used as a fluorinating agent for laboratory scalesynthesis. If HF is used, the only byproduct is HCl. The synthesizedF1S₃MN compound is washed from the solid salt with hexane, distilled,dried with CaO, and distilled again.

Scheme 2 depicts a synthesis scheme for F1S₃MN using NH₄FHF as afluorinating agent. Using Karstedt's catalyst(Platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex solution,Cat. No. 479519, Sigma-Aldrich, St. Louis, Mo.), about 3% substitutionon the secondary carbon occurs, generating isoF1S₃MN. The isoF1S₃MN hasa lower boiling point than F1S₃MN, and most of it can be separated byfractional distillation.

Scheme 3 depicts an alternative, shorter synthesis scheme for F1S₃MNusing a Cl1S₃MN intermediate. The Cl1S₃MN intermediate can be obtainedby Gelest, Inc. (Product Code SIC2452.0, 11 East Steel Road,Morrisville, Pa.). Use of the Cl1S₃MN intermediate reduces the timespent during synthesis.

Scheme 4 depicts yet another synthesis scheme for F1S₃MN. As with Scheme1, [F] indicates a fluorinating agent, such as HF, NH₄FHF, or otherfluorinating agent. The use of HF as fluorinating agent in thissynthesis scheme will not give solid byproducts, so there is no need ofhexane extraction and filtration of solid. The only byproduct is HCl.

Scheme 5 depicts yet another synthesis scheme for F1S₃MN. As with Scheme1, [F] indicates a fluorinating agent, such as HF, NH₄FHF, or otherfluorinating agent.

Synthesis of F1S₃MN:

In the preferred route, allyl cyanide is heated to about 100° C. with asmall amount of Karstedt's catalyst. Dimethylchlorosilane was addeddropwise and refluxed 4 hours. After cooling to room temperature, themixture was fluorinated using 1 mol equivalent of ammonium hydrogenfluoride at room temperature. Cold hexane was added to the mixture, thesolid was filtered off, and the solvent evaporated. Calcium oxide wasadded to the crude product and it was distilled under vacuum between45-55° C. at 0.4 Torr to yield the desired product, F1S₃MN.

Determination of the Electrochemical Stability of OrganosiliconMaterials:

Computational chemistry methods were used to calculate electrochemicalproperties of various organosilicon molecules. We used the GAMESSprogram developed by the Gordon research group at Iowa State Universityfor the Density Function Theory (DFT) molecular orbital calculations.The HOMO (highest occupied molecular orbital) and LUMO (lowestunoccupied molecular orbital) energy levels, which correlate to thereduction and oxidation potentials of compounds, were calculated at theB3LYP/DZV level.

The oxidative stability of electrolytes containing organosiliconsolvents was determined using linear sweep voltammetry (LSV) or cyclicvoltammetry (CV) in a 3-electrode cell. A platinum microelectrode wasused as the working electrode with lithium metal as both the counter andreference electrode. The potential of the system was increased from theopen circuit voltage (OCV) to 6 or 8V (vs. Li/Li+) at a scan rate of 10mV/s. The resulting current density (mA/cm2) was recorded at eachpotential with a higher current indicating an oxidative reaction (i.e.,lower oxidative stability). For the linear sweep voltammetry, 8V wasused as a final potential to evaluate the fundamental oxidativestability of the material across a wider voltage range. For the cyclicvoltammetry, 6V was used to evaluate the material across multiple scansunder potentials more relevant to traditional battery applications.Multiple scans were conducted in the cyclic voltammetry experiments todetermine the reversibility/irreversibility of any reactions observed.

The reductive stability of electrolytes containing organosiliconsolvents was determined using linear sweep voltammetry (LSV) in a3-electrode cell. A glassy carbon electrode was used as the workingelectrode with lithium metal as both the counter and referenceelectrode. The potential of the system was decreased from the opencircuit voltage (OCV, typically 3V) to 0.1V (vs. Li/Li+) at a scan rateof 10 mV/s. The resulting current density (mA/cm²) was recorded at eachpotential with a greater current indicating a reduction reaction (i.e.,lower reductive stability). Two scans were conducted to evaluate if thereductive processes were reversible or irreversible (i.e., passivating).

Electrochemical Stability of F1S₃MN:

Molecular orbital diagrams for F1S₃MN and F1S₃M2, not shown, reveal thatthe energy difference between the highest occupied molecular orbital(HOMO) and the lowest unoccupied molecular orbital (LUMO) is greater forF1S₃MN (9.07 eV) than for F1S₃M2 (8.20 eV). F1S₃MN also has a higheroxidation potential (−8.75 eV) than F1S₃M2 (−6.84 eV).

FIGS. 1A and 1B depict the oxidation stability of F1S₃MN with LiPF₆,LiBF₄, or LiTFSI in current density (mA/cm²) versus voltage (V vs.Li/Li⁺). The oxidation stability was tested at room temperature with aworking electrode as Pt, a counter electrode as Li, a referenceelectrode as Li/Li⁺, and a sweep rate of 10 mV/s. FIG. 1B depicts aclose-up of the same data shown in FIG. 1A. The F1S₃MN-LiPF₆ electrolyteexhibited the best oxidation stability, having a current density of 1mA/cm² at 7.3 V compared to a current density of 1 mA/cm² at 6.8 V and6.2 V for F1S₃MN-LiBF₄ and F1S₃MN-LiTFSI, respectively.

FIGS. 2A and 2B depict the reduction stability of F1S₃MN with LiPF₆,LiBF₄, or LiTFSI in current density (mA/cm²) versus voltage (V vs.Li/Li⁺). The reduction stability was tested at room temperature with aworking electrode as Pt, a counter electrode as Li, a referenceelectrode as Li/Li⁺, and a sweep rate of 10 mV/s. FIGS. 2A and 2B aretwo separate scans. The F1S₃MN-LiPF₆ electrolyte exhibited the bestreduction stability.

FIGS. 3A and 3B depict the oxidation stability of F1S₃MN or F1S₃M2 with1M LiPF₆ in current density (mA/cm²) versus voltage (V vs. Li/Li⁺). Theoxidation stability was tested at room temperature with a workingelectrode as Pt, a counter electrode as Li, a reference electrode asLi/Li⁺, and a sweep rate of 10 mV/s. FIG. 3B depicts a close-up of thesame data shown in FIG. 3A. F1S₃MN demonstrated improved oxidationstability with respect to F1S₃M2.

FIG. 4 depicts the reduction stability of F1S₃MN or F1S₃M2 with 1M LiPF₆compared to a carbonate control electrolyte with LiPF₆ in currentdensity (mA/cm²) versus voltage (V vs. Li/Li⁺) in two separate scans.The reduction stability was tested at room temperature with a workingelectrode as Pt, a counter electrode as Li, a reference electrode asLi/Li⁺, and a sweep rate of 10 mV/s. F1S₃MN demonstrated less resistanceto reduction compared to F1S₃M2.

Determination of Thermal Stability of Neat Solvents & FormulatedElectrolytes:

The thermal stability of both the neat organosilicon solvents and theelectrolyte compositions were determined as follows: Approximately 0.75mL of liquid sample was heated in a sealed cell under an argon purge.The Argon purge was carried to an atmospheric sampling mass spectrometerwhere any gas phase impurities and/or decomposition products can bedetected at very low levels using electron impact mass spectrometry(EI-MS). The sample was held for 1 hour at pre-determined temperaturelevels that are relevant for battery applications (30, 55, 70, 100, 125,150, 175, and 200° C.). The gas phase decomposition products wereidentified by comparing fragmentation patterns obtained from the EI-MSto NIST standards. Following the heating experiment (anddetection/collection of all gas phase products), the remaining liquidsample was analyzed via NMR spectroscopy for a quantitative analysis ofthe extent of decomposition. Multiple nuclei were examined to fullyanalyze all components of the system, including the organosiliconsolvent, any carbonate co-solvents, all additives, and the lithium salt(if present).

Thermal Stability of F1S₃MN:

FIGS. 5A and 5B depict the thermal stability of F1S₃MN with LiPF₆.F1S₃MN-LiPF₆ electrolyte (batch ZP815-01) was exposed to temperaturesranging from 30° C. to 175° C. and analyzed by electron impact massspectrometry (EI-MS) and nuclear magnetic resonance spectroscopy (NMR)for gas and liquid decomposition products, respectively. Thetemperatures at which salient peaks appeared are annotated. F1S₃MNshowed no significant gas and/or liquid phase decomposition up to 175°C. Me₂SiF₂ appeared at temperatures of 100-125° C. at 81 m/z, and MeSiF₃appeared at temperatures of 150-175° C. at 85 m/z. However, the 81 m/zand 85 m/z peaks appeared inconsistently at 100-175° C. Furthermore, ¹HNMR analysis showed no decomposition after heating to 175° C. Therefore,F1S₃MN does not show consistent decomposition up to 175° C. FIG. 5Adepicts a close-up of the same data shown in FIG. 5B.

FIG. 6 depicts the thermal stability of F1S₃M2 with LiPF₆. F1S₃M2-LiPF₆electrolyte was exposed to temperatures ranging from 30° C. to 150° C.and analyzed by mass spectrometry for decomposition products. Thetemperatures at which salient peaks appeared are annotated. F1S₃M2showed decomposition at temperatures ≧125° C. Decomposition productsincluded Me₂SiF₂ and 1,4-dioxane. ¹H NMR analysis showed approximately6% decomposition at 150° C. These results in combination with thosediscussed in relation to FIG. 5A and FIG. 5B indicate that F1S₃MN ismore thermally stable than F1S₃M2.

FIG. 7 depicts the thermal stability of F1S₃MN with LiTFSI.F1S₃MN-LiTFSI electrolyte was exposed to temperatures ranging from 30°C. to 185° C. and analyzed by mass spectrometry for decompositionproducts. The temperatures at which salient peaks appeared areannotated. Gas phase peaks were observed at temperatures ≧150° C. Peaksat 117 and 102 matched patterns observed for F1S₃MN-LiBF₄ electrolyteand neat solvent (see FIGS. 8 and 9).

FIG. 8 depicts the thermal stability of F1S₃MN with LiBF₄. F1S₃MN-LiBF₄electrolyte was exposed to temperatures ranging from 30° C. to 200° C.and analyzed by mass spectrometry for decomposition products. Thetemperatures at which salient peaks appeared are annotated. Gas phasepeaks were observed at temperatures ≧175° C. Peaks at 117 and 102matched patterns observed for neat solvent and F1S₃MN-LiTFSI electrolyte(see FIGS. 7 and 9). ¹H NMR analysis showed no fluorinated decompositionproducts and <0.5% of a non-fluorinated hydrolysis product.

FIG. 9 depicts the thermal stability of neat F1S₃MN. F1S₃MN electrolytewas exposed to temperatures ranging from 30° C. to 195° C. and analyzedby mass spectrometry for decomposition products. The temperatures atwhich salient peaks appeared are annotated. Gas phase peaks wereobserved at temperatures ≧150° C. At 150° C., Me₂SiF₂ was observed(96/81 m/z), but other peaks were not associated with this product. ¹HNMR analysis showed no fluorinated decomposition products and <0.5%hydrolysis.

The above data show that F1S₃MN is the most thermally stable OS solventwith LiPF₆.

Synthesis of DF1S₃MN:

Commercial 3-cyanopropyldichloromethylsilane (CAS No. 1190-16-5; SigmaAldrich, St. Louis, Mo., US) was fluorinated with ammonium bifluoride atroom temperature. Cold hexane was then added to the mixture. The solidwas filtered off and the solvent evaporated. Calcium oxide was added tothe crude product. The solvent was distilled under vacuum between 35-45°C. at 0.4 Torr to yield the desired product in very high purity (˜99.8%)and approximately 90% yield.

Synthesis of DF1S₂MN:

Acrylonitrile was mixed with N,N,N′,N′-tetramethylethylenediamine andcopper (I) oxide in a flask and heated to 60° C. Dichloromethylsilanewas then added dropwise and refluxed overnight. After cooling to roomtemperature, the mixture was distilled under vacuum (43° C., 0.2 Torr)to yield the dichloro intermediate (DCl1S₂MN). The intermediate wasfluorinated using 1.2 mol equivalents of ammonium hydrogen fluoride atroom temperature or 1.2 mol equivalents of sodium hydrogen fluoride at130° C. Dichloromethane was then added and the solid filtered off. Thesolvent was evaporated and the crude product was distilled under vacuum.Triethylamine and molecular sieves were added to the product anddistilled under vacuum between 25-33° C. at 0.1 Torr to yield thedesired product at extremely high purity (>99%) at approximately 75%yield.

Thermal Stability of DF1S₃MN:

FIG. 10 depicts the thermal stability of DF1S₃MN with LiPF₆.DF1S₃MN-LiPF₆ electrolyte (ZP990-01) was exposed to temperatures from30° C. to 150° C. and analyzed by electron impact mass spectrometry(EI-MS) and nuclear magnetic resonance spectroscopy (NMR) for gas andliquid decomposition products, respectively. DF1S₃MN showed nosignificant gas and/or liquid phase decomposition up to 150° C.

Differential Scanning calorimetry (DSC) Evaluation for Thermal AbuseTolerance:

DSC measurements were conducted with F1S₃MN and carbonate basedelectrolytes in the presence of de-lithiated cathode materials toevaluate potential thermal abuse tolerance effects that could translateto safety advantages in a full cell format. Higher onset temperature,lower total heat output and lower peak heat output are all effects thatsuggest improved thermal abuse behavior in full format cells.

FIG. 11 depicts the thermal stability of F1S₃MN with LiPF₆ and variouscarbonate co-solvents and is compared to a carbonate control electrolytewith LiPF₆. Cells containing each electrolyte were charged to 4.25V andthen disassembled. The lithium nickel cobalt aluminum oxide (NCA)cathode was rinsed with diethylene carbonate and allowed to dry. Eachsample containing 5 mg of active material and 2 mg of fresh electrolytewas hermetically sealed into a stainless steel DSC pan. DSC scans at arate of 2° C./min showed that the carbonate control electrolyte reactedat a much lower onset temperature than any of the organosiliconelectrolyte blends. Additionally, the electrolyte where organosilicon issubstituted for EMC has a much lower peak heat output than the controlelectrolyte.

Preparation of Electrolytes:

Blending of electrolytes is completed inside a moisture-free (<5 ppm)and oxygen-free (<20 ppm) argon glove box. All electrolyte components,including solvents, salts, and additives have been properly dried beforeblending and are stored in the glove box. Solvent moisture is monitoredperiodically by Karl Fischer measurement to ensure moisture levels aremaintained at <20 ppm. Generally, solvents are weighed first into aseparate vial and mixed until homogeneous. 70% of the solvent is addedto a volumetric flask. Lithium (or other) salt is added slowly andstirred by magnetic stir bar until completed dissolved. Any otheradditives (i.e. VC, LiBOB) are then added slowly and stirred until thesolution is homogeneous. The stir bar is removed and a portion of theremaining solvent is added to complete the volumetric requirement. Thestir bar is placed back into the volumetric flask and the electrolyte isstirred until homogeneous. After blending is complete the electrolyte isdispensed into a dried vial or alternate container for storage.

Performance of F1S₃MN in Lithium Ion Cells:

FIG. 12 depicts the discharge capacity at 30° C. of cells containingvarious electrolyte solvents. Three different electrolyte solvents weretested in Lithium Ion cells over a series of cycles at different C-ratesin a 2032-size coin cell assembly (assembly stack as in FIG. 13)containing a graphite anode, a lithium nickel cobalt aluminum oxide(NCA) cathode, and “2500”-type separator from Celgard, LLC (Charlotte,N.C.). The three electrolyte solvents were: (1) control EPA6 carbonateelectrolyte comprising 1:1 by volume ethylene carbonate (EC) and diethylcarbonate (DEC) (triangles); (2) an F1S₃MN-based electrolyte comprising79% F1S₃MN, 20% EC, 1 M LiPF₆, and solid electrolyte interphase(SEI)-forming additives (squares); and (3) an F1S₃M2-based electrolyte,comprising 79% F1S₃M2, 20% EC, 1 M LiPF₆, and SEI-forming additives(circles). As shown in FIG. 12, the F1S₃MN-based electrolyte isequivalent to EPA6 at the 4C rate.

FIG. 14 depicts the discharge capacity at 55° C. of cells containing thesame electrolytes as shown in, and described for FIG. 12. The cells wereassembled in the same manner and cycled at a C/2 rate. As shown in FIG.14, the F1S₃MN-based solvent had improved cycling stability at 55° C.compared to both the carbonate control and the F1S₃M2-based electrolyte.

Performance of F1S₃MN and DF1S₂MN in Electrical Double-Layer CapacitorsCells:

Symmetric electrical double layer capacitors (EDLC) were assembled intoCR2032 coin cells as depicted in FIG. 15. A glass fiber separator (AP40,Merck Millipore) was sandwiched between two pieces of AC clothelectrode, with 100 μL electrolyte added to the separator.Tetraethylammonium tetrafluoroborate (TEA-BF₄, Alfa Aesar, 99%) andtetrabutylphosphonium hexafluorophosphate (TBP-PF₆, Sigma Aldrich,≧99.0%) were used as the salts. Organosilicon solvents of F1S₃MN (99.4%)and DF1S₂MN (99.8%) were made by Silatronix. Acetonitrile (AN, SigmaAldrich, anhydrous, 99.8%) was used as a co-solvent. Zorflex FM10 100%activated carbon (AC) cloth from Calgon carbon was used for bothelectrodes. FM10 has 1000-2000 m2/g surface area, 0.5 mm thickness, and120 g/m2 area density. The AC cloth was punched to 15 mm diameter discs,and used directly as electrodes without any binder or conductiveadditives.

The performance of EDLC cells was tested by cyclic voltammetry (CV)using a Biologic BMP300 potentiostat. The temperature as control in anoven with variation as ±0.1° C. The cyclic voltammetry (CV) responses ofthe EDLC cells was conducted between 0 and 3 V at a scan rate of 10mV/s. A normalized specific capacitance, C, was derived according to thefollowing equation [1,2]:

$C = \frac{i}{mv}$where i is the current, v is the scan rate, m is the mass of oneelectrode.

FIG. 16 shows the cyclic voltammograms of EDLC cells with OSelectrolytes containing TEA-BF₄ salt. Electrolyte ZX1193 included 1.0MTEA-BF₄ dissolved in 70 volume percent DF1S₂MN and 30 volume percentacetonitrile. Electrolyte ZX1190 included 0.8M TEA-BF₄ dissolved intoblended DF1S₂MN and acetonitrile solvents, 60:40 by volume. The EDLCcells with both electrolyte formulations showed the regular andsymmetric features to the 0 horizontal axis, indicating a non-redox orfaradic properties of the cell.

FIG. 17 shows the cyclic voltammograms of EDLC cells with ZX1170electrolyte and ZX1184 electrolyte containing TBP-PF₆ salt. ElectrolyteZX1170 has 1.2M TBP-PF₆ dissolved into F1S₃MN, and electrolyte ZX1184has 1.2M TBP-PF₆ dissolved into DF1S₂MN. The non-redox or faradicproperties can also be observed from the EDLC cells with bothelectrolyte ZX1170 and ZX1184 formulations.

1ND1N Synthesis:

Scheme 6 depicts a synthesis scheme for 1ND1N. 1ND1N cannot bechemically dried with sodium (Na), calcium oxide (CaO), or calciumhydride (CaH₂).

Electrochemical Stability of 1ND1N:

The molecular orbital diagram for 1ND1N and 1ND1, not shown, reveal theenergy difference between the highest occupied molecular orbital (HOMO)and the lowest unoccupied molecular orbital (LUMO) for 1ND1N is 7.88 eV(LUMO=0.21 eV; HOMO=−7.88 eV) and for 1ND1 is 8.36 eV (LUMO=1.63 eV;HOMO=−6.73 eV). 1ND1N has great oxidation stability but lower reductionresistance than 1ND1.

FIG. 18 depicts the oxidation stability of 1ND1N with 1M LiPF₆ or 1MLiTFSI in current density (mA/cm²) versus voltage (V vs. Li/Li⁺). Theoxidation stability was tested at room temperature with a workingelectrode as Pt, a counter electrode as Li, a reference electrode asLi/Li⁺, and a sweep rate of 10 mV/s.

FIG. 19 depicts the reduction stability of 1ND1N with 1M LiPF₆ or 1MLiTFSI in current density (mA/cm²) versus voltage (V vs. Li/Li⁺). Thereduction stability was tested at room temperature with a workingelectrode as Pt, a counter electrode as Li, a reference electrode asLi/Li⁺, and a sweep rate of 10 mV/s. Two separate scans for eachelectrolyte are shown.

FIGS. 20A and 20B depict current density (mA/cm²) versus voltage (V vs.Li/Li⁺) for cycling scans with 1ND1N and 1M LiPF₆ or 1M LiTFSI from 0 to6 V and from 6 to 0 V. FIG. 20A depicts a first cycle. FIG. 20B depictsa second cycle.

FIGS. 21A and 21B depict the oxidation stability of F1S₃MN or 1ND1N with1M LiPF₆ in current density (mA/cm²) versus voltage (V vs. Li/Li⁺). Theoxidation stability was tested at room temperature with a workingelectrode as Pt, a counter electrode as Li, a reference electrode asLi/Li⁺, and a sweep rate of 10 mV/s. FIG. 21B depicts a close-up of thesame data shown in FIG. 21A. The F1S₃MN-LiPF₆ electrolyte had a currentdensity of 1 mA/cm² at 7.3 V, and the 1ND1N-LiPF₆ electrolyte had acurrent density of 1 mA/cm² at 7.2 V.

FIGS. 22A and 22B depict the oxidation stability of F1S₃MN or 1ND1N with1M LiTFSI in current density (mA/cm²) versus voltage (V vs. Li/Li⁺). Theoxidation stability was tested at room temperature with a workingelectrode as Pt, a counter electrode as Li, a reference electrode asLi/Li⁺, and a sweep rate of 10 mV/s. FIG. 22B depicts a close-up of thesame data shown in FIG. 22A. The F1S₃MN-LiTFSI electrolyte had a currentdensity of 1 mA/cm² at 6.2 V, and the 1ND1N-LiTFSI electrolyte had acurrent density of 1 mA/cm² at 6.5 V.

Thermal Stability of 1ND1N:

FIG. 23 depicts the thermal stability of neat 1ND1N. 1ND1N was exposedto temperatures ranging from 30° C. to 189° C. and analyzed by massspectrometry for decomposition products. 1ND1N showed no liquid or gasphase decomposition products up to 189° C. ¹H NMR showed ˜%5decomposition.

FIG. 24 depicts the thermal stability of 1ND1N with LiPF₆. 1ND1N-LiPF₆electrolyte was exposed to temperatures ranging from 30° C. to 150° C.and analyzed by mass spectrometry for decomposition products. Thetemperatures at which salient peaks appeared are annotated. 1ND1N showedgas phase decomposition ≧70° C., but no vigorous reaction was observedup to 150° C. Me₂SiF₂ (81 m/z) (96 g/mol) and a peak at 52/53 m/zsuspected as being acrylonitrile (53 g/mol) appeared at a temperaturesof 125-150° C. No 1,4-dioxane gas was observed at 150° C. ¹H NMRanalysis showed that 50.6% 1ND1N remained at 125° C. and 58% remained at150° C. At 125° C., presence of 39.7% fluorinated product F1NM1N (vs.2.3% in unheated sample, 1.6% Me₂SiF₂ (vs. 0% in unheated sample), and2.95% hydrolysis (vs. 5.5% in unheated sample) was observed. At 150° C.,presence of 41% fluorinated product F1NM1N (vs. 2.3% in unheatedsample), 1.7% Me₂SiF₂ (vs. 0% in unheated sample), and 5.0% hydrolysis(vs. 5.5% in unheated sample) was observed.

To identify the peaks observed at 52/53 m/z upon heating 1ND1N-LiPF₆ at125-150° C., the mass spectrum profile for heated 1ND1N-LiPF₆ wascompared with the mass spectrum profiles of National Institute ofStandards and Technology (NIST) standards for 2-propenenitrile andhydrogen cyanide. FIG. 25A depicts a close-up of the mass spectrumprofile as described with respect to FIG. 24 from 24-30 m/z. FIG. 25Bdepicts a close-up of the mass spectrum profile as described withrespect to FIG. 24 from 49-55 m/z. The temperatures at which salientpeaks in FIGS. 25A and 25B appeared are annotated. The peaks at 51, 52,and 53 m/z in FIG. 25B indicate that acrylonitrile is likely present.The presence of HCN cannot be definitively confirmed or disconfirmed dueto the presence of peaks at 26 and 27 m/z in the NIST spectra. Thespectrum in FIG. 25A shows a greater peak intensity at 26 m/z comparedto 27 m/z, which supports the presence of acrylonitrile. However, themagnitude of the peak at 27 m/z is greater than expected foracrylonitrile alone.

FIG. 26 depicts the thermal stability of 1ND1N with LiTFSI, vinylenecarbonate (VC) and lithium bis(oxalato)borate (LiBOB).1ND1N-LiTFSI-VC-LiBOB was exposed to temperatures ranging from 30° C. to185° C. and analyzed by mass spectrometry for decomposition products.1ND1N-LiTFSI-VC-LiBOB showed no gas phase decomposition products up to185° C. ¹H NMR showed an increase in hydrolysis from 3% (in the unheatedsample) to 18.7% (after heating), which was likely due to a delay beforethe NMR analysis was performed.

FIG. 27 depicts the thermal stability of 1ND1N with LiBF₄. 1ND1N-LiBF₄was exposed to temperatures ranging from 30° C. to 125° C. and analyzedby mass spectrometry for decomposition products. The temperatures atwhich salient peaks appeared are annotated. Gas phase products evolvedat ≧30° C. As expected, Me₂SiF₂ (81 m/z) (96 g/mol) was observed. Noacrylonitrile was observed. ¹H NMR showed 3.7% hydrolysis and 34.2%fluorinated products (3 sets of peaks). ¹⁹F NMR showed that all F in thesystem was bonded to Si. No BF₄ remained. There was insufficient F tofully decompose 1ND1N (˜5M 1ND1N versus 4 M F).

While no acrylonitrile was observed by mass spectrometry in heated1ND1N-LiBF₄ samples, it was observed in unheated control (70 ppm). Thisindicates 1ND1N is not stable with LiBF₄ at room temperature. NMRanalysis revealed that heating does little to increase decomposition, asshown in the following table:

¹H (MeSi peak) hydrolysis fluorination Before Heating 3% 43% AfterHeating 4% 34%Performance of 1ND1N in Cells:

FIG. 28 depicts the discharge capacity of cells containing variouselectrolytes at a variety of C-rates. The electrolyte solvents were: (1)1ND1N; (2) 1ND1N with 20% ethylene carbonate (EC) co-solvent (1ND1N_EC);and (3) 1ND2 with 20% EC co-solvent (1ND2_EC). All formulations alsocontained SEI-forming additives and 1 M LiPF₆ salt. As shown in FIG. 28,20% EC co-solvent improved the performance of 1ND1N. With 20% ECco-solvent, 1ND1N showed diminished performance compared to 1ND2 at allC-rates.

FIG. 29 depicts the discharge capacity of cells containing various otherelectrolyte solvents. The electrolyte solvents were: (1) 1ND1N with 20%EC co-solvent, 1 M LiPF₆ and SEI-forming additives (1ND1N-EC-LiPF₆,shown as 1ND1N_EC in FIG. 29); (2) 1ND1N with 20% EC co-solvent, 1 MLiTFSI and SEI-forming additives (1ND1N-EC-LiTFSI, shown as 1ND1N_T inFIG. 29); and (3) 1ND2 with 20% EC co-solvent, 1 M LiPF₆ and SEI-formingadditives (1ND2-EC-LiPF₆, shown as CP597-07 in FIG. 29). The1ND1N-EC-LiPF₆ combination and the 1ND1N-EC-LiTFSI combination showedperformance comparable to the 1ND2-EC-LiPF₆ combination.

FIGS. 30A and 30B depict the discharge capacity of cells containing a1ND1N-LiPF₆-based electrolyte or a 1ND1N-LiTFSI-based electrolyte,respectively, at a variety of C-rates. For each experiment, a CR2032coin cell with a Saft America (Cockeysville, Md.) NCA cathode, agraphite anode, and a 2500 separator from Celgard, LLC (Charlotte, N.C.)was used. The cells were charged with aconstant-current/constant-voltage (CCCV) procedure at C/5, C/2, 1C or 2Crates to 4.1 V. The cells were discharged each cycle to 3.0 V with aconstant current at the same rate that they were charged. In FIG. 30A,the 1ND1N-LiPF₆-based electrolyte solution included 1 M LiPF₆ and 1ND1N(batch ZP780-01), and the charging/discharging was performed at 30° C.or 55° C. In FIG. 30B, the 1ND1N-LiTFSI-based electrolyte solutionincluded 1 M LiTFSI and 1ND1N, batch (ZT781-01), and thecharging/discharging was performed at 30° C., 55° C., or 70° C. As shownin FIGS. 30A and 38B, the 1ND1N-LiTFSI-based electrolyte displayedbetter rate capability than the 1ND1N-LiPF₆-based electrolyte.

Physical Properties of OS Solvents and Electrolyte Solutions:

Table 1, above, shows physical properties of selected organosilicon (OS)compounds (1S₃MN, F1S₃MN, F1S₃cMN, DF1S₃MN, DF1S₂MN, and F1S₃M2) as neatsolvents and formulated electrolyte solutions. Table 2, above, showsphysical properties of neat 1ND1N, 1ND1, 1ND2, and F1S₃MN and variouselectrolyte compositions containing them. In both tables, theconductivity has units of mS/cm, the viscosity has units of cP, and theflash point is in degrees Celsius.

Proton (¹H) NMR spectra taken in CDCl₃ for 1ND1N, 1ND1N, DF1S₂MN,DF1S₃MN, F1S₃cMN, and 1S₃MN are presented in FIGS. 31-36, respectively.For selected compounds containing a fluorine atom, ¹⁹F-NMR data werecollected in CDCl₃ and DMSO-d₆. The results are tabulated below:

¹⁹F-NMR in CDCl₃ F1S₃MN −162.3 ppm, ¹J(¹⁹F,²⁹Si) = 280 Hz isoF1S₃MN−166.6 ppm, ¹J(¹⁹F,²⁹Si) = 284 Hz DF1S₃MN −135.3 ppm, ¹J(¹⁹F,²⁹Si) = 296Hz TF1S₃MN −136.8 ppm, ¹J(¹⁹F,²⁹Si) = 280 Hz DF1S₂MN −135.2 ppm,¹J(¹⁹F,²⁹Si) = 296 Hz

¹⁹F-NMR in DMSO-d₆ F1S₃MN −159.2 ppm, ¹J(¹⁹F,²⁹Si) = 279 HzConclusions:

F1S₃MN and 1ND1N are both suitable for use as electrolyte solvents inLi-ion batteries. F1S₃MN and DF1S₂MN have demonstrated function aselectrolyte solvents in EDLC devices.

F1S₃MN shows very high thermal stability (measured by ¹H NMR) with allsalts tested. F1S₃MN shows the highest thermal stability of any OS withLiPF₆ (175° C.), with no observed decomposition. F1S₃MN does produce gasphase products as neat solvent, with LiBF₄, and with LiTFSI. These gasphase products can be attributed to low levels of F1S₃MN evaporation.F1S₃MN shows increased voltage stability (higher oxidation potentialwith wide window) compared to F1S₃M2. F1S₃MN provides equivalentperformance as EPA6 up to a rate of 4C. LiBOB has limited solubility inF1S₃MN (<0.03M) without co-solvent, but LiBOB solubility improves(>0.1M) with use of co-solvent (i.e. 20% EC). The decomposition productsof F1S₃MN are Me₂SiF₂ and MeSiF₃, both of which are gases.

1ND1N shows no gas phase decomposition as a neat solvent or incombination with LiTFSI electrolyte up to 185-190° C. The combination of1ND1N with LiTFSI electrolyte shows promise up to 70° C. and higher.1ND1N with LiPF₆ is more thermally stable than either 1ND1 or 1ND2 withLiPF₆. It forms acrylonitrile above 125° C. Like other non-spacercompounds, 1ND1N reacts at room temperature with LiBF₄. However, thereis insufficient F to fully decompose the 1ND1N, and it does not formacrylonitrile. The rate performance of 1ND1N is slightly lower than1ND2.

What is claimed is:
 1. An electrolyte composition comprising a compoundof Formula III,

wherein R¹, R², and R³ are the same or different and are independentlyselected from the group consisting of C₁ to C₆ linear or branched alkyland fluorine, and wherein at least one of R¹, R², or R³ is fluorine;“Spacer” is selected from the group consisting of C₃ to C₆ linear orbranched alkylene, alkenylene, or alkynylene; and R⁴ is selected fromthe group consisting of cyano (—CN), cyanate (—OCN), isocyanate (—NCO),thiocyanate (—SCN) and isothiocyanate (—NCS); in combination with alithium-containing salt.
 2. The electrolyte composition of claim 1,wherein R⁴ is cyano.
 3. The electrolyte composition of claim 1, whereinR¹, R², and R³ are selected from the group consisting of C₁ to C₃ alkyl,and fluoro.
 4. The electrolyte composition of claim 1, wherein at leasttwo of R¹, R², and R³ are fluorine.
 5. The electrolyte composition ofclaim 1, wherein “Spacer” is a C3 to C₄ linear or branched alkylene. 6.An electrochemical device comprising an electrolyte composition asrecited in claim
 1. 7. The electrochemical device of claim 6, wherein R⁴is cyano.
 8. The electrochemical device of claim 6, wherein R¹, R², andR³ are selected from the group consisting of C₁ to C₃ alkyl, and fluoro.9. The electrochemical device of claim 6, wherein at least two of R¹,R², and R³ are fluorine.
 10. The electrochemical device of claim 6,wherein “Spacer” is a C3 to C₄ linear or branched alkylene.